It looks like this ebook is done with bookdown
:
When hovering over a reference or footnote, the information is displayed already:
What is the name of this feature?
The current online version of Causal Inference: The Mixtape
is actually done using Quarto, not {bookdown}
. And AFAIK, it seems Quarto makes use of Tippy.js
to show footnotes on hover.
However, bookdown::bs4_book()
has similar functionality. It has an argument footnotes_inline
which is by-default TRUE
.
footnotes_inline
: By default, footnotes will be set inline and shown on hover. Set toFALSE
to keep footnotes at the bottom of the page with links.
As an example of bookdown::bs4_book
, checkout the footnote used in this section of Mastering Shiny
book